Thermometer trimming method and apparatus

ABSTRACT

Apparatus for trimming a thermometer to remove excess mercury including a fixture mounted on a laser device in energy-receiving relationship therewith. The fixture includes a housing having an open end through which a thermometer-holding device is adapted to move between a thermometer-inserting position and a thermometeraligned position wherein the thermometer is aligned with the laser beam. A light trap is provided for sealing the open end of the housing when the thermometer holding device is in the thermometer-aligned position to prevent the leakage of energy from the laser device through the open end of the housing. A method for trimming a thermometer also is disclosed.

United States Patent Duffy et al.

[ 1 Feb.8, 1972 Primary Examiner-J. V. Truhe Assistant Examiner-LawrenceA. Rouse Attorney--Yuter and Fields AND APPARATUS [72] Inventors: JosephJ. Duffy, Northport; Stuart Donald [54] THERMOMETER TRlMMING METHODSims, Huntington, both of NY.

[73] Assignee: Hadron, lne., Westbury, NY.

[ ABSTRACT Apparatus for trimming a thermometer to remove excess mer-[22] Filed: Nov. 26, 1968 [21] Appl.No.: 779,197

cury including a fixture mounted on a laser device in energyreceivingrelationship therewith. The fixture includes a housing having an openend through which a thermometer-holding aser be am. A light trap isprovided for sealing the open end of the housing when the ther- L Mt 0 wd td Um. 1]] 2100 6 555 5 [[l. 1.

UNITED STATES PATENTS 219/121 L A method for trimming a thermometer alsois disclosed.

3,210,171 3,364,087 1/1968 Solomon et a1.. 3,472,998 10/1969 Popick et17 Claims, 3 Drawing Figures VARIABLE ENER'GY STORAGE CAPACITOR BANKPOWER SUPPLY r\ INVENTORS JOSEPH J. DUFFY S. DONALD SIMS ATTORNEYS.

PAIENIEBFEB 8B7? 3.641.307

l I l l I 3 I l I I l 1 INVENTORS JOSEPH J. DUFFY s. DONALD SIMS MATTORNEYS.

THERMOMETER TRIMMING METHOD AND APPARATUS This invention relatesgenerally to a thermometer-trimming method and apparatus therefor and,more particularly, pertains to an apparatus for and a method of removingexcess mercury from a thermometer.

Inherent in the manufacture of mercury thermometers for laboratory orclinical use or the like is the need to remove the excess mercury fromthe capillary tube after it has been filled. One method which is widelyused is referred to as the so-called gas torch method wherein eachthermometer is placed in a clamp and a gas torch is applied to thethermometer at the point at which the mercury column is to be severed.The heat from the torch causes the mercury to vaporize at that point toseparate the excess from the column of mercury. Thereafter, thethermometer is placed in a centrifuge which drives the excess mercuryinto a ball at the top of the tube which is then severed from tube andthe thermometer sealed.

It is obvious that the above-described procedure is entirely unsuitedfor mass production techniques as it is extremely time consuming andhighly unreliable. That is, the heat content of the gas torch usuallyvaries within limits so that the operator must apply the torch fordifferent periods of time depending on the energy of the torch at aparticular instant. Moreover, the services of a skilled person arerequired for this operation thereby increasing the cost of such devices.Additionally, if the torch is applied for too long an interval the glasswill be damaged. Hence a relatively high rate of damaged thermometersare produced by this method.

Another equally disadvantageous method presently in use for trimmingthermometers includes heating the reservoir of the thermometer to apreselected temperature and drawing off the excess mercury. Thethermometer is then cooled to a predetermined temperature and the heightof the mercury column is noted. This procedure is continued until themercury reaches a desired height at which point the thermometer issealed. Thus, it is obvious that this latter procedure is even more timeconsuming and unreliable than the former method described above.

Accordingly, an object of the present invention is to provide animproved apparatus and method for quickly and efficiently removing theexcess mercury from a column of mercury in a thermometer and the like.

A more specific object of this invention is to provide an apparatuswhich includes a laser device for accurately trimming a thermometer.

Another object of the present invention resides in the novel details ofconstruction which provide an apparatus of the type described whichincludes a fixture for accurately aligning a thermometer with a laserbeam for severing a column of mercury in a thermometer at a preselectedpoint.

A further object of the invention is the provision ofthermometer-trimming apparatus which is simple in construction andreliable in operation.

Another object of the present invention is to providethermometer-trimming apparatus which always supplies the same magnitudeof energy to the thermometer and to eliminate variations in the intervalof time the energy is supplied to the thermometer.

A further object of the invention is the provision of athermometer-trimming apparatus of the type described wherein thepossibility of damage to the glass thermometer tube is substantiallyeliminated.

Accordingly, an apparatus constructed in accordance with the presentinvention includes a fixture for aligning a thermometer with a laserbeam which includes a housing having at least one open end. Mountingmeans for mounfing the housing on the laser device inenergy-receivingrelationship therewith is provided and thermometer-holding means whichincludes a thermometer retainer for orienting a thermometer in apreselected position is similarly provided. The thermometerholding meansis movable through said open end between a first position in which saidthennometer retainer is positioned external to the housing for theinsertion of a thermometer and a second position in which saidthermometer retainer is positioned within the housing to align thethermometer with the laser beam. The thermometer-holding means furtherincludes a light trap which sealingly engages the housing when thethermometer-holding means is in the second position to prevent theleakage of energy from the laser device through the open end of thehousing.

A feature of the present invention is the provision ofthermometer-trimming apparatus wherein a laser beam strikes eachthermometer at the same point with the same amount of energy therebysevering the excess mercury from the remainder of the mercury column toprovide an efficient and reliable device.

Another feature of the present invention, is to provide a housing whichprevents the leakage of light from the laser beam when a thermometer isin position to receive energy from the laser.

Other features and advantages of the present invention will become moreapparent from a consideration of the following detailed description whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective exploded view, partially in diagrammatic form,of a thermometer-trimming apparatus constructed in accordance with thepresent invention;

FIG. 2 is a partial sectional front view thereof; and

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2.

An apparatus constructed in accordance with the present invention isdesignated generally by the reference numeral 10 in the FIGS. andincludes the laser head or laser device 12, and a fixture which isdesignated generally by the reference numeral 14. The fixture 14includes a mounting 16 which is adapted to be connected with the laserdevice 12, and a housing 18, which is connected with the mounting 16. inthe discussion which follows, the laser device 12 will not be describedin detail. It is to be understood, however, that the mounting 16 ismounted on the laser device 12 in such a manner that the beam 20 fromthe laser device 12 passes through a lens, which is designated generallyby the reference numeral 22, received in the mounting 16.

More specifically, as shown in FIG. 3, the mounting 16 includes amounting plate 24 which is connected to the laser head or laser device12 by any conventional means as by screws or the like. Connected to themounting plate 24 by screws 26 is a housing retaining member 28. Themember 28 is provided with an outwardly extending continuous peripheralflange 30 which defines a recessed wall 32. Provided in the mountingplate 24 and the housing retaining member 28, is a through bore 34 whichreceives the lens 22 therein. The lens 22 includes a lens barrel 36which receives a focusing lens ar rangement 38 therein. The lens barrel36 is maintained in place by a set screw 40 which is received in athreaded opening in the lens 22. It will now be obvious that themounting plate 24 is connected to the laser head or laser device 12 withthe axis of the lens 22 aligned with the optical axis of the laser beam20.

Mounted on the recessed wall 32 of the housing retaining member 28 aretransversely spaced microswitches 42 and 44. The microswitches 42 and 44are connected to the laser power supply 46 by respective leads 48 and50. The power supply 46 is connected to the laser head 12 through avariable energy storage capacitor bank 52 by a lead 54. As noted indetail below, one of the microswitches 42 or 44 must be operated beforethe power supply 46 can apply energy to the laser head 12.

Housing 18 includes a top wall 56, a bottom wall 58, a front wall 60which is integral with the walls 56 and 58, and opposed end walls 62 and64. The side of the housing 18 opposite the wall 60 is open and thewalls 62, 56, 64, and 58 adjacent to the open end of the housing 18 areprovided with a continuous recessed groove 66 which receives theperipheral flange 30 of the housing retaining member 28 to form a rabbetjoint therewith. The rabbet joint fonned by the elements 30, 66 providea lighttight connection between the housing 18 and the housing retainingmember 28. The housing 18 may be connected to the member 28 by anyconventional means as by screws (not shown) extending through theretaining member 28 and terminating in threaded apertures (not shown) inmember 18.

The end walls 62 and 64 are provided with aligned elongated rectangularopenings 68 and 70, respectively (FIG. 2). The opening 68 is defined bya recessed flange 72. Similarly, the opening 70 is defined by a recessedflange 74.

Slidably received in the housing 18 is a thermometer holder which isdesignated generally by the reference numeral 76. As shown in FIG. 2,the thermometer holder 76 includes a righthand portion 78 and aleft-hand portion 80. The right-hand portion 78 is defined by an outerwall 82 and an intermediate wall 84. The left-hand portion 80 is definedby the intermediate wall 84 and an outer wall 86. Since the portions 78and 80 are identical in construction, only the portion 78 will bedescribed in detail. However, the same reference numerals will indicateidentical elements in the respective portions.

More specifically, a bottom rod 88 extends between the walls 82 and 86and passes through an aperture 90 in the wall 84. The rod 88, which, inpractice, is fabricated from nylon or the like, is provided with alongitudinal groove 92 which receives a pin 94 therein extendinginwardly from the front wall 60. The pin 94 coacting with the groove 92guide the thermometer holder 76 in its movement in the housing 18, asnoted in detail below. The top of the rod 88 is provided with alongitudinal recess 96. Received in the recess 96 are respective blocks98 and 100. The blocks 98 and 100 include respective lower sections 102and 104 which meet each other along a central edge 106; The respectiveupper sections 108 and 110 of the blocks 98 and 100 are of smallerdimension than the respective lower sections to define substantiallyrectangular opening 112. The blocks 98 and 100 are maintained in placeby screws 114 which extend upwardly through the rod 88 into therespective blocks and are recessed within the rod 88. A bar 116 isreceived on the upper edges of the blocks 98 and 100 and is connectedthereto by screws 118 which are recesses within the bar. As shown inFIG. 2, the rod 88 is in sliding engagement with the edges of theflanges 72 and 74 and the bar 116 of the portion 78 is in slidingengagement with the upper edge of the flange 72. Similarly, the bar 116of the portion 80 is in sliding engagement with the upper edge of theflange 74. Additionally, screws 120 connect the upper sections 108 and110 of the blocks to the juxtaposed walls.

Thermometer retaining means is provided for retaining thermometers inthe left and right-hand portions 80 and 78 of the thermometer holder 76.To be more specific, the edges of the blocks adjacent the central line106 are provided with complementary formed bevels to provide V-shapedslot 121. The lower abutting comers of the blocks 98 and 100 are cutaway to provide an opening 122 which is adapted to receive the reservoirof the thermometer. Centrally located in the opening 122 and extendingthrough the rod 88 is a threaded bore 124 which receives a set screw 126therein. The set screw 126 is operable to position the thermometer withrespect to the laser beam 20, as noted in detail below.

Provided in the blocks 98 and 100 are opposed transverse aligned bores 128 and 130, respectively. Received within the bores 128 and 130 arerespective springs 132 which bias balls 134 toward each other. The bores130 are positioned so that the balls 134 engage the edges of athermometer which is received in the slot 121 to retain the thermometerin position. The springs 132 resiliently maintain the balls in positionbut permit movement of the balls outwardly to facilitate the easyinsertion or removal of the thermometer into the slot.

As shown in FIG. 2, the outer wall 82-is sized and positioned to abutthe flange 72 defining the opening 68 when the righthand portion 78 ofthe thermometer holder 76 is received within the housing 18 to provide alight trap to prevent energy from the laser beam from exiting throughthe opening 68. Ad-

ditionally, the intermediate wall 84 is sized to engage the innersurface of the flange 74 defining the opening 70 when the right-handportion 78 of the thermometer holder 76 is received within the housing18 to provide a light trap which prevents energy from the laser beamfrom exiting through the opening 70. On the other hand, when theleft-hand portion of the thermometer holder 76 is received within thehousing 18, the wall 86 is sized to engage the outer surface of theflange 74 to provide a light trap which prevents the energy from thelaser beam 20 from exiting through the opening 70. Additionally, whenthe left-hand portion 80 is received in the housing 18, the intermediatewall 84 is sized to engage the inner surface of the flange 72 to providea light trap which prevents the light from the laser beam 20 fromexiting through the opening 68. As shown in FIG. 3, an outwardlyextending pin 136 is received in the wall 84 and is positioned to engagethe microswitch 42 or 44 to operate the same. More specifically, the pin136 is positioned in the wall 84 so as to engage the microswitch 42 andoperate the same when the right-hand portion 78 of the thermometerholder 76 is completely received within the housing 18. To put thisanother way, the microswitch 42 will only be operated when the lighttraps formed by the walls 82 and 84 and the respective flanges 72 and 74are closed to prevent light from the laser head 12 from exiting throughthe end openings in the housing. Likewise, the pin 136 is positioned sothat the microswitch 44 will be operated only when the left-hand portion80 of the thermometer holder 76 is fully received within the housing 18and the light traps formed by the walls 86 and 84 and the respectiveflanges 74 and 72 are closed to prevent energy from the laser beam 20from again exiting through the end openings in the housing.

In the description of the operation of the apparatus 10 which follows,it will be assumed that the elements are positioned as shown in FIG. 2.Accordingly, a thermometer is inserted into the left-hand portion 80 ofthe thermometer holder 76 by inserting the thermometer into the V-shapedslot 121. As noted hereinabove, it is assumed that the thermometer whichis to be trimmed is triangular in cross section so that it will fitsnugly in the slot 121. However, if the thermometer has a cross sectionother than triangular, the slot 121 may be changed accordingly. Thereservoir or bulb of the thermometer is positioned in the opening 122.The thermometer is moved downwardly into the bore 124 in the rod 88until the bottom of the bulb of the thermometer rests against the setscrew 126. The set screw 126 is then moved upwardly or downwardly byrotating the same in the threaded bore 124 until the point marking thedesired height of the mercury column in the thermometer is in the sameplane as the optical axis of the laser beam 20. That is, the set screw126 provides a means for raising or lowering the thermometer so that thelaser beam will strike the mercury column at the desired point. Once theset screw 126 has been set for desired height of the mercurythermometer, it does not have to change for the remaining thermometersof the same type. The balls 134 retain the thermometer in the slot 121in the manner described above.

After the thermometer has been inserted into the thermometer holder 76,the thermometer holder is slid to the right, as taken in FIG. 2.Accordingly, the left-hand portion 80 of the holder will enter thehousing 18 and the right-hand portion 78 will exit through the opening68. The thermometer holder 76 continues moving toward the right untilthe intermediate wall 84 engages the flange 72 in a lighttightengagement and the outer wall 86 engages the flange 74 in a lighttightengagement. Accordingly, the thermometer will now be substantiallycentrally located within the housing 18. Simultaneously with thelighttight closing of the open ends of the housing 18, the pin 136engages the microswitch 44 to allow triggen'ng ofthe laser head. Thus,power will be applied to the laser head or device 12 through thevariable energy storage capacitor bank 52 to produce a pulse of energyfrom the laser head 12.

FIG. 1 illustrates this operation for a thermometer T which is receivedin the right-hand portion 78 of the thermometer holder 76. Thus, thepulse of energy or laser beam 20 passes through the lens 22 and strikesthe thermometer at the desired height in accordance with the setting ofthe set screw 126, as noted above. The lens 22 is adjusted to bring thelaser beam 20 to a line focus which is perpendicular to the column ofmercury in the capillary of the thennometer T. Accordingly, the mercurywill vaporize at this point to break the mercury column.

The variable energy storage capacitor bank 52 is adapted to vary theinput pulse energy and therefore the amount of energy in the laser beam20. The energy storage is adjusted so that the energy which strikes thethermometer T will be sufficient to drive the excess mercury into a bulbB at the top of the thermometer T. Once the variable storage capacitorbank has been set to deliver a particular pulse of energy, it requiresno further adjustment for thermometers of the same type. It is to benoted that the laser beam 20 in no way affects the glass thermometer butonly has an effect on the mercury column by separating the excessmercury from the remainder of the mercury column.

It is to be noted that when one portion of the thermometer holder 76 isreceived within the housing 18, the other portion lies outside thehousing and is easily accessible. Thus, while one thermometer is beingsubjected to the laser beam another thermometer may be loaded into theother portion of the thermometer holder. Thus, if the portion 80 isreceived within the housing 18, a thermometer may be inserted into theslot 121 in the right-hand portion 78 of the thermometer holder 76.After the thermometer within the housing has been subjected to the beamfrom the laser head 12, (the thermometer in the lefthand portion 80 inthe example chosen) the holder 76 is moved toward the left as taken inFIG. 2. Thus, the thermometer loaded into the portion 78 is positionedwithin the housing 18. When the openings 68 and 70 are again closed bythe respective walls 82 and 84 in lighttight engagement therewith,respectively, the pin 136 engages the microswitch 42 to again operatethe power supply 46. Hence, the thermometer T now received in theportion 78 will be subjected to the laser beam.

At this time, the thermometer which has been operated upon by the laserbeam is removed from the left-hand portion 80 of the thermometer holder76 and the lower portion of the glass tube is severed from the bulb Bcontaining the excess mercury and is sealed to provide an accuratelytrimmed thermometer. It is to be noted that if the mercury has not beendriven into the bulb B, the thermometer may be taken and put in acentrifuge to drive the mercury into the bulb B in the conventionalmanner. Thereafter, the bulb B may be severed and the thermometersealed.

In practice, a lowenergy normal mode ruby laser may be utilized as thelaser device or laser head 12.

Accordingly, a method for trimming a thermometer and an apparatustherefor has been described which accurately and reliably trims athermometer to remove excess mercury from the mercury column in a quickand efficient manner without causing any damage to the thermometer tube.

What is claimed is:

l. A fixture for aligning a thermometer with a laser beam including ahousing having at least one open end, mounting means for mounting saidhousing on a laser device in energyreceiving relationship therewith,thermometer-holding means including a thermometer retainer for orientinga thermometer in a preselected position and being movable through saidopen end 7 between a first position in which said thermometer retaineris positioned external to said housing for the insertion and removal ofa thermometer and a second position in which said thermometer retaineris positioned within said housing to align the thermometer with a laserbeam, said fixture further including a light trap for sealing saidhousing when said thermometer-holding means is in said second positionto prevent the leakage of energy from said laser device through saidopen end.

2. A fixture as in claim 1, and a lens received in said mounting meansfor focusing the beam from the laser device on the thermometer.

3. A fixture as in claim 1, in which said thermometer-holding meansincludes height adjusting means for selectively adjusting the height ofthe thermometer received in said thermometer retainer with respect tothe laser beam.

4. A fixture as in claim 1, and switch means responsive to the secondposition of said thermometer-holding means for energizing the laserdevice.

5. A fixture as in claim 1, in which said thermometer-holding means isprovided with an end wall, said end wall being sized and positioned toengage said housing in a lighttight engagement to provide said lighttrap.

6. A fixture as in claim 5, in which said housing includes a recessedflange surrounding said open end, said end wall engaging said recessedflange when said thermometer-holding means is in said second position toprovide said light trap,

7. A fixture as in claim 1, in which said housing includes opposed openends, means for slidably mounting said thermometer-holding means on saidhousing for movement through said open ends, said thermometer retainerbeing a first thennometer retainer, said thermometer-holding meansincluding a second thermometer retainer connected to said firstthermometer retainer whereby said second thermometer retainer isreceived within said housing to align a thermometer with the laser beamwhen said first thermometer retainer is in said first position and ispositioned external of said housing for the insertion and removal of athermometer when said first thermometer retainer is in said secondposition, and light trap means for engaging said housing in a lighttightengagement when said first thermometer retainer is in said firstposition and said second thermometer retainer is positioned within saidhousing.

8. A fixture as in claim 7, and switch means operable to energize thelaser device when said first thermometer retainer is in said first orsaid second position.

9. A fixture as in claim 7, in which said thermometer-holding meansincludes first and second end walls associated with said first andsecond thermometer retainers, and an intermediate wall separating saidfirst and second thermometer retainers and slidably received in saidhousing, said light trap means including said second end wall and saidintermediate wall which are sized and positioned to engage said housingadjacent the open ends thereof to provide light seals adjacent therespective open ends.

10. Apparatus for trimming a thermometer comprising laser means forproducing a laser beam when energized, selectively operable energizingmeans for energizing said laser means, a fixture connected to said lasermeans for aligning a thermometer with said laser beam, said fixtureincluding a housing having at least one open end, thermometer-holdingmeans including a first thermometer retainer for orienting a thermometerin a preselected position and being movable through said open endbetween a first position in which said thermometer retainer ispositioned external to said housing for the insertion and removal of athermometer and a second position in which said thermometer retainer ispositioned within said housing to align the thermometer with said laserbeam, said thermometer-holding means including light trap means forpreventing passage of the laser beam through said open end when saidfirst thermometer retainer is in said second position.

11. Apparatus as in claim 10, in which said thermometerholding meansincludes a second thermometer retainer connected to said firstthermometer retainer and being positioned external of said housing whensaid first thermometer retainer is in said second position and beingpositioned within said housing when said first thermometer retainer isin said first position.

12. Apparatus as in claim 11, in which said housing is provided withopposed open ends, said first thermometer retainer being adapted to movethrough one of said open ends, said second thermometer retainer beingadapted to be moved through the other of said open ends.

13. Apparatus as in claim 12, in which said light trap means includes anintermediate wall between said first and second thermometer retainers,said intermediate wall being sized and positioned to engage said housingadjacent said one open end when said first thermometer retainer is insaid first position to light-tightly seal said one opening, saidintermediate wall engaging said housing adjacent the other open end tolighttightly seal said other open end when said first thermometerretainer is in said second position.

14. Apparatus as in claim 13, in which said light trap means furtherincludes a first end wall connected to said first thermometer retainerand a second end wall connected with said second thermometer retainer,respective recessed flanges adjacent to the open ends of said housing,said end wall associated with said first thermometer retainer engagingthe recessed flange associated with said one open end of said housingwhen said first thermometer retainer is in said second position toprevent the passage of the laser beam therethrough, said second end wallengaging the flange adjacent said other open end when said firstthermometer retainer is in said first position to prevent the passage ofsaid laser beam through said other open end.

15. Apparatus as in claim 11, and adjusting means in said first andsecond thermometer retainers for selectively adjusting the height ofthermometers received therein.

16. Apparatus as in claim 10, and a lens for bringing said laser beam toa line focus perpendicular to a thermometer received in said first andsecond thermometer retainers.

17. Apparatus as in claim 11, in which said energizing means includesswitch means responsive to the first and second position of said firstthermometer retainer for energizing said laser means.

1. A fixture for aligning a thermometer with a laser beam including ahousing having at least one open end, mounting means for mounting saidhousing on a laser device in energy-receiving relationship therewith,thermometer-holding means including a thermometer retainer for orientinga thermometer in a preselected position and being movable through saidopen end between a first position in which said thermometer retainer ispositioned external to said housing for the insertion and removal of athermometer and a second position in which said thermometer retainer ispositioned within said housing to align the thermometer with a laserbeam, said fixture further including a light trap for sealing saidhousing when said thermometer-holding means is in said second positionto prevent the leakage of energy from said laser device through saidopen end.
 2. A fixture as in claim 1, and a lens received in saidmounting means for focusing the beam from the laser device on thethermometer.
 3. A fixture as in claim 1, in which saidthermometer-holding means includes height adjusting means forselectively adjusting the height of the thermometer received in saidthermometer retainer with respect to the laser beam.
 4. A fixture as inclaim 1, and switch means responsive to the second position of saidthermometer-holding means for energizing the laser device.
 5. A fixtureas in claim 1, in which said thermometer-holding means is provided withan end wall, said end wall being sized and positioned to engage saidhousing in a lighttight engagement to provide said light trap.
 6. Afixture as in claim 5, in which said housing includes a recessed flangesurrounding said open end, said end wall engaging said recessed flangewhen said thermometer-holding means is in said second position toprovide said light trap.
 7. A fixture as in claim 1, in which saidhousing includes opposed open ends, means for slidably mounting saidthermometer-holding means on said housing for movement through said openends, said thermometer retainer being a first thermometer retainer, saidthermometer-holding means including a second thermometer retainerconnected to said first thermometer retainer whereby said secondthermometer retainer is received within said housing to align athermometer with the laser beam when said first thermometer retainer isin said first position and is positioned external of said housing forthe insertion and removal of a thermometer when said first thermometerretainer is in said second position, and light trap means for engagingsaid housing in a lighttight engagement when said first thermometerretainer is in said first position and said second thermometer retaineris positioned within said housing.
 8. A fixture as in claim 7, andswitch means operable to energize the laser device when said firstthermometer retainer is iN said first or said second position.
 9. Afixture as in claim 7, in which said thermometer-holding means includesfirst and second end walls associated with said first and secondthermometer retainers, and an intermediate wall separating said firstand second thermometer retainers and slidably received in said housing,said light trap means including said second end wall and saidintermediate wall which are sized and positioned to engage said housingadjacent the open ends thereof to provide light seals adjacent therespective open ends.
 10. Apparatus for trimming a thermometercomprising laser means for producing a laser beam when energized,selectively operable energizing means for energizing said laser means, afixture connected to said laser means for aligning a thermometer withsaid laser beam, said fixture including a housing having at least oneopen end, thermometer-holding means including a first thermometerretainer for orienting a thermometer in a preselected position and beingmovable through said open end between a first position in which saidthermometer retainer is positioned external to said housing for theinsertion and removal of a thermometer and a second position in whichsaid thermometer retainer is positioned within said housing to align thethermometer with said laser beam, said thermometer-holding meansincluding light trap means for preventing passage of the laser beamthrough said open end when said first thermometer retainer is in saidsecond position.
 11. Apparatus as in claim 10, in which saidthermometer-holding means includes a second thermometer retainerconnected to said first thermometer retainer and being positionedexternal of said housing when said first thermometer retainer is in saidsecond position and being positioned within said housing when said firstthermometer retainer is in said first position.
 12. Apparatus as inclaim 11, in which said housing is provided with opposed open ends, saidfirst thermometer retainer being adapted to move through one of saidopen ends, said second thermometer retainer being adapted to be movedthrough the other of said open ends.
 13. Apparatus as in claim 12, inwhich said light trap means includes an intermediate wall between saidfirst and second thermometer retainers, said intermediate wall beingsized and positioned to engage said housing adjacent said one open endwhen said first thermometer retainer is in said first position tolight-tightly seal said one opening, said intermediate wall engagingsaid housing adjacent the other open end to light-tightly seal saidother open end when said first thermometer retainer is in said secondposition.
 14. Apparatus as in claim 13, in which said light trap meansfurther includes a first end wall connected to said first thermometerretainer and a second end wall connected with said second thermometerretainer, respective recessed flanges adjacent to the open ends of saidhousing, said end wall associated with said first thermometer retainerengaging the recessed flange associated with said one open end of saidhousing when said first thermometer retainer is in said second positionto prevent the passage of the laser beam therethrough, said second endwall engaging the flange adjacent said other open end when said firstthermometer retainer is in said first position to prevent the passage ofsaid laser beam through said other open end.
 15. Apparatus as in claim11, and adjusting means in said first and second thermometer retainersfor selectively adjusting the height of thermometers received therein.16. Apparatus as in claim 10, and a lens for bringing said laser beam toa line focus perpendicular to a thermometer received in said first andsecond thermometer retainers.
 17. Apparatus as in claim 11, in whichsaid energizing means includes switch means responsive to the first andsecond position of said first thermometer retainer for energizing saidlaser means.